A well-known problem in regions having hard water (i.e., water containing a high level of calcium or magnesium ions) is the formation of scale deposits. Particularly in applications where there are high levels of carbonate and/or phosphate ions, the formation of Ca/Mg scales of these species can lead to buildup that causes an unsightly residue (“film”). The terms “carbonate scale” and “phosphate scale” refer to salts of carbonate and phosphonate with calcium, magnesium, or other metal ions.
Carbonate scale and phosphate scale are particularly troublesome in machine dishwashing applications because they have a tendency to cause unsightly residues or films on dishware, tableware, and especially glassware. This phenomenon is widely known as “hard water film.” In general, the presence of phosphates and carbonates are desirable in machine dishwashing compositions because of their cleaning power or building power. As a result, “anti-filming technologies” to reduce the formation of carbonate scale or phosphate scale resulting from automatic dishwashing have been described in the literature.
Exemplary anti-filming technologies have utilized polycarboxylates such as polyacrylates and polymethacrylates. See U.S. Pat. No. 5,591,703. Polycarboxylate technologies assist in the reduction of hard water filming in automatic dishwashing, as well as in more general water treatment applications. Another class of anti-filming materials to reduce phosphate and to some degree carbonate scale is the sulfonate/carboxylate copolymers. See U.S. Pat. No. 5,547,612 and U.S. Pat. No. 6,395,185. Commercially available examples of sulfonate/carboxylate copolymers include Alcosperse 240™ from Alco Chemical and Acusol 586™ from Rohm and Haas Company. The copolymers can be derived from combinations of sulfonate-containing and/or carboxylate-containing ethylenically unsaturated monomers, such as acrylic acid, methylallylsulfonic acid, ethoxylate esters of acrylic acids, and variations thereof.